<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计数的循环变量泄露为全局变量</title>
</head>
<body>
    <script>
        var str = "welcome";
        for(var i = 0;i < str.length;i++){
            console.log(str[i]);
        }

        console.log(i);  //7
    </script>
</body>
</html>